Consider a scenario where you are needing to specify catalog

Consider a scenario where you are needing to specify catalog spur gears for a design. Specifically you are looking to order gears from the table below from the Martin Sprocket and Gear. Inc. catalog sheet The electric motor which will serve as the prime mover for this application rotates at 1, 200 rpm. The output shaft must rotate as close as possible to 500 rpm without dropping below this value. If a pinion with 24 teeth has been chosen to attach to the electric motor shaft, how many teeth should the mating gear have? Assume that interference does not need checked.

Solution

Speed ratio required = W_output / W_input     = 500 / 1200   = 5 / 12

Therefore the gear ratio must be 5 / 12 as well

no of teeth on mating gear / no of gear on pinion   = 1 / speed ratio

no of teeth on mating gear    = 12 * 24 / 5   = 57.6

from the catalog we have a gear with 54 teeth, so we can use this gear without going below rated 500 rpm.